CVE-2026-84365: Hono Incomplete Fix For CVE-2026-39408: `toSSG()` Vulnerability

MODERATE
Advisory Identifier: GHSA-gqvv-2mrq-wpjv
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CVSS 6.5
CWE-22
Published
Advisory Summary

CVE-2026-84365 is a MODERATE (CVSS 6.5) incomplete fix for cve-2026-39408: `tossg()` vulnerability (CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')) affecting Hono libraries in the npm ecosystem. The issue involves incomplete fix for cve-2026-39408: `tossg()` still writes files outside the output directory. Remediation is available by upgrading affected packages to version 4.13.5.

CVE-2026-84365 at a Glance

CVE Identifier CVE-2026-84365
GHSA Identifier GHSA-gqvv-2mrq-wpjv
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Affected Product Hono
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 6.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction Required (UI:R)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity High (I:H)
Availability None (A:N)

How to Fix CVE-2026-84365

To remediate this vulnerability, upgrade all affected Hono dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

hono fixed: 4.13.5 
npm install hono@4.13.5
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls hono

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-84365, inspect your project dependencies using npm:

npm ls hono

Analyze the terminal output to locate any version of Hono in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.13.5), your application is affected.

Note: The npm ls hono command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal'), where the product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. In Hono, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary The fix released for CVE-2026-39408 does not cover every traversal sequence. `toSSG()` can still write files outside the configured output directory when a route parameter contains consecutive parent-directory segments. ### Details Static site generation builds each output path from the route path and the values supplied through `ssgParams`, then verifies that the result stays inside the output directory. That check normalizes the path with the same routine that built it, and the routine did not fully collapse runs of consecutive parent-directory segments. A value carrying enough of them produces a path the check accepts, but the filesystem resolves outside the output directory. The earlier fix handled a single parent-directory segment, so it blocks the sequence reported at the time while leaving longer runs unhandled. The check also treated output directories that differ only in how they are rooted as equivalent. This arises when an application generates a static site from route parameter values it does not fully control — slugs coming from a CMS, an API, or user submissions. ### Impact A value reaching `ssgParams` from an untrusted source can cause build output to be written outside the intended output directory, carrying whatever content the route handler produced. This may lead to: - files being created or overwritten elsewhere in the build environment - generated artifacts or deployment output being altered This affects build-time static site generation only; request-time routing is not affected. Applications whose `ssgParams` values are entirely developer-controlled are not affected.

CVE-2026-84365 Affected Hono Versions

1 component(s)
Fixed Versions:
4.13.5
Product / Package Ecosystem Affected Versions Fixed Version
hono
npm/hono
npm
< 4.13.5
4.13.5

References

GitHub Advisory / Wiki ADVISORY
https://github.com/honojs/hono/security/advisories/GHSA-gqvv-2mrq-wpjv
NVD — CVE-2026-84365 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-84365
Security Fix Commit FIX COMMIT
https://github.com/honojs/hono/commit/3a67f7f3997e1437d108f7bcba2dbcee2df69221
Hono Source Repository REPOSITORY
https://github.com/honojs/hono
Hono Release RELEASE
https://github.com/honojs/hono/releases/tag/v4.13.5

Frequently Asked Questions

What is CVE-2026-84365?
CVE-2026-84365 is a security vulnerability in Hono involving Incomplete fix for CVE-2026-39408: `toSSG()` still writes files outside the output directory under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal').
Which Hono versions are affected?
Affected versions include releases prior to 4.13.5 across affected packages: hono.
What version fixes CVE-2026-84365?
Upgrading to 4.13.5 (or the latest patched release for your respective branch) resolves the vulnerability.
Is hono affected?
Yes, hono is affected in releases prior to 4.13.5. Upgrade your dependency to 4.13.5 or later.
What is the CVSS score of CVE-2026-84365?
CVE-2026-84365 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N.
What CWE is associated with CVE-2026-84365?
CVE-2026-84365 is classified under CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') (The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.).
How can I check npm dependencies for CVE-2026-84365?
Run the dependency tree command: 'npm ls hono'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gqvv-2mrq-wpjv",
  "modified" : "2026-09-08T21:23:51Z",
  "published" : "2026-09-08T21:23:51Z",
  "aliases" : [ "CVE-2026-84365" ],
  "summary" : "Hono: Incomplete fix for CVE-2026-39408: `toSSG()` still writes files outside the output directory",
  "details" : "### Summary\n\nThe fix released for CVE-2026-39408 does not cover every traversal sequence. `toSSG()` can still write files outside the configured output directory when a route parameter contains consecutive parent-directory segments.\n\n### Details\n\nStatic site generation builds each output path from the route path and the values supplied through `ssgParams`, then verifies that the result stays inside the output directory. That check normalizes the path with the same routine that built it, and the routine did not fully collapse runs of consecutive parent-directory segments. A value carrying enough of them produces a path the check accepts, but the filesystem resolves outside the output directory.\n\nThe earlier fix handled a single parent-directory segment, so it blocks the sequence reported at the time while leaving longer runs unhandled. The check also treated output directories that differ only in how they are rooted as equivalent.\n\nThis arises when an application generates a static site from route parameter values it does not fully control — slugs coming from a CMS, an API, or user submissions.\n\n### Impact\n\nA value reaching `ssgParams` from an untrusted source can cause build output to be written outside the intended output directory, carrying whatever content the route handler produced.\n\nThis may lead to:\n\n- files being created or overwritten elsewhere in the build environment\n- generated artifacts or deployment output being altered\n\nThis affects build-time static site generation only; request-time routing is not affected. Applications whose `ssgParams` values are entirely developer-controlled are not affected.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "hono"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.13.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/security/advisories/GHSA-gqvv-2mrq-wpjv"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-84365"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/commit/3a67f7f3997e1437d108f7bcba2dbcee2df69221"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/honojs/hono"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/honojs/hono/releases/tag/v4.13.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-08T21:23:51Z",
    "nvd_published_at" : "2026-09-01T21:18:47Z"
  }
}